By a modification of our original retrograde intrabiliary injection technique, it is now possible to demonstrate the process of filtration of certain solutes placed in the biliary tree. One purpose of the studies will be to characterize this filtration process as to the relationship between the size of the solute and the quantity of solute retained in the biliary tree. The site at which the solute is retained is speculated to be the canalicular membrane. The study will be done by using non-metabolized sugars of increasing molecular weights including dextrans and polyethylene glycols. Also, we have preliminary evidence of a transport system for absorbing glucose from the biliary tree. This system will be studied as 1- and 3-methyl substituted D-glucose uptake. Modification of uptake by phlorizin treatment will be included. Furthermore, studies on the modification of the permeability of the biliary tree by treatment with bile acids and estrogen will be pursued. Such modification will be reflected in changes in recovery (retention) of the trace marker compounds along with changes in intrabiliary pressures. Intrabiliary pressures will be measured as in our earlier publication.